The present invention relates to a rolling mill in which conical rolls are arranged with axes that are inclined in relation to each other and cooperating with a piercing mandrel establishing a rolling gap therewith for forming tubular stock out of solid billets, with a declining wall thickness and increasing diameter in the direction of rolling and under utilization of disks or sheaves for guiding the rolling stock in front of or in a plane transverse to the axes of rolling which runs through points of minimum distance between the rolls, which disks have axes parallel to that plane.
German printed patent application No. 21 56 595 discloses a rolling mill with obliquely positioned rolls of the type referred to above and including specifically such guide disks which project through two lateral windows in rolling stand and reach into the working range of the rolls. In lieu of such driven guide disks one can use guide bars which are adjustable by means of levers and transversely to the direction of rolling. Such a guide structure is for example disclosed in "Stahl und Eisen" 53, 19, pages 465-470.
German Pat. No. 641 375 suggests the utilization of rolls or bars in a rolling mill with oblique rolls to be placed between these rolls and as an alternative for piercing or stretch reducing. In a later development, piercing is carried through so called Diescher disks with axes of rotation transverse to the axes of rolling. These disks are usually driven at a peripheral speed which exceeds the longitudinal speed of the rolled stock.
If a solid billet is pierced in a rolling mill with oblique rolls then special requirements arise for guiding the rolled stock. Particularly if drastic widening occurs to a diameter having a 1.5-fold value of the original billet. Rolling mill constructions proposed for this purpose are shown in German Pat. Nos. 418 002 or 505 250 using conical rolls.